1092 GEOLOGY OF OHIO. 
ammonia; if a clear solution was not obtained, it was reprecipitated by 
acidifying with nitric acid and adding more molybdic acid solution. 
The resulting precipitate was washed again in dilute “molybdate” solu- 
tion, redissolved with ammonia, the solution thus obtained being pre- 
cipitated with an ammoniacal solution of magnesic chloride, care being 
taken to secure a gradual crystallization of the ammonio-magnesic 
phosphate by a cautious addition of the “ magnesia mixture ” accom- 
panied by stirring. The other elements were determined in 100 c. c¢. 
(= 1 gramme) by first precipitating the iron, alumina and phosphorus, 
by boiling the almost neutral solution, with the addition of sodic acetate. 
The filtrate, after the separation of the manganese as dioxide by adding 
bromine water and heating for some hours, was used for the determina- 
tion of lime and magnesia as in limestone. 
The precipitate of manganese dioxide, produced by the bromine, 
was washed well, and if in very small amounts, as was usually the case, 
was ignited and weighed as manganese proto sesquioxide (Mn, O,); if 
present in larger amounts, it was dissolved and converted into phosphate 
and weighed as such. 
The precipitate of ferric oxide and alumina was redissolved in 
hydrochloric acid, diluted, boiled, precipitated with ammonia, and the 
precipitate weighed. From the weight of this the ferric oxide and 
phosphorus was deducted, what remained being the alumina. 
Sulphur was invariably determined in a separate portion of the ore 
by fusing with a mixture of sodic-nitrate and carbonate, extracting with 
water, and after evaporation with hydrochloric acid to separate silica, 
filtering and precipitating with baric chloride. 
Moisture was determined by drying a portion at 100° C, and weigh- 
ing the loss. Combined water was determined by heating to redness 
in a platinum crucible, then igniting slowly fora long time, in some 
cases with the addition of a little nitric acid so as to convert all iron 
oxides to the ferric state, and then weighing the loss. 
The phosphorus is only completely gotten into solution by fusing 
the residues as described; weighing the “insoluble silicious matter” 
direct!y, and not treating for phosphorus, is, in the experience of our 
laboratory, sure to involve loss of that element. 
In case of “blackbands” and similar highly carbonaceous ores, the 
organic matter and the water were expelled by careful burning and 
